Battery charger protection circuit

Discussion in 'Power Electronics' started by jtn, Apr 2, 2017.

  1. jtn

    Thread Starter New Member

    Mar 27, 2017
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    Hello everyone. I just joined this forum. I try to design a charger protection circuit based on the logic that when battery is fully charge, the voltage is in floating mode and the charge current is from full charge current to almost 0A. In normal mode the relay connect the charger to the 12V lead acid battery. Once the battery is fully charge, voltage is in floating condition > 14V (?) and charge current collapsed to 0A, Transistor Q2 will turn on relay coil and disconnect the charger. Could you please review if the circuit is making sense. Thanks
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,752
    2,857
    No schematic. You may need a moderator to let you post one before you have more posts. I'll try to let them know.
     
  3. jtn

    Thread Starter New Member

    Mar 27, 2017
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    Sorry. I forgot to attach the schematic. Thanks
     
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    8,149
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    Its far too over complicated,!!
    no need for Q2, use the fet Q1 to switch on the relay, also your opamp configured for voltage sensing will be in reverse and wont allow it to start charging, and it's not got hysteresis.....
     
    Last edited: Apr 3, 2017
  5. LesJones

    Well-Known Member

    Jan 8, 2017
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    Also it does not latch off after the battery voltage exceeds 14 volts. The battery voltage will drop below 14 volts a short time after the charger is disconnected and it will switch back to charging the battery.

    Les.
     
  6. jtn

    Thread Starter New Member

    Mar 27, 2017
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    I thougth the op-amp is configured in the way that will latch off Q2 in normal operation. I will eliminate Q2 an simplify the circuit
    Thank you for your comment
     
  7. jtn

    Thread Starter New Member

    Mar 27, 2017
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    0
    The logic here is I need both conditions (Voltage and Current) in order to latch on Q2. Even voltage is fall back below 14V but current is at 0A, X1-out is at 0V and still holing Q1 Off. Should I remove 2 andd D5 ? Thank you
     
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